**6.1. Human waste into the marine ecosystem**

There are 33 megacities in the world, and 21 of them are situated on coastlines. If one considers that at least 50% of the world's population lives in urban areas, where wastewater management systems are often outdated or completely inadequate, the sensitive urban coastal ecosystems are under serious threat [66]. It is estimated that over 90% of wastewater in developing countries is discharged, without any form of treatment into the marine environment, as well as into rivers and lakes. In more developed countries, at least primary treatment is required before discharging wastewater into the environment. Consequently, millions of litres of raw waste water or digested sludge are released into the marine environment. This practice often represents an alternative to tertiary treatment, as well as the most inexpensive means of disposal. The effluents released in ocean outfalls contain faecal material from domestic waste water and industrial discharges with persistent toxic substances and heavy metals. Harmful impacts include risk to public health, beaches, marine animals, as well as contamination of shellfish. Moreover, this release of high volumes of organic matter into the marine environment or contributory rivers also results in eutrophication, which leads to so-called dead zones in the seas and oceans. Approximately 245 000 km2 of marine environment is thought to be affected by these dead zones [66, 69].

Bitton's [69] book summarized several global surveys of enteric pathogens in contaminated sea water. A number of authors reported enteric viruses of the coast of countries such as Brazil, France, Israel, Italy, Spain and the USA. The virus types found included polioviruses, coxsackie A and B viruses, echo-, adeno- and rotaviruses. These were also detected in sediments in close proximity of sewage outfalls, and found to prevail for extended periods of time. Also, pathogenic bacteria such as *Salmonella* and *Vibrio cholerae* were reported in coastal waters near ocean outfalls. Several illnesses among the human population have been reported as a result of exposure to bacteria from sewage contaminated water, including spp. of *Aeromonas, Leptospira, Mycobacterium, Legionella, Pseudomonas, Vibrio* and *Staphylococcus.*  Adenoviruses were also associated with these illnesses, as well as the protozoa, *Naegleria fowleri* and *Acanthamoeba.* These microbes were found in cases of wound infections, skin and subcutaneous lesions, dermatitis, subcutaneous abscesses, septicaemia, conjunctivitis, pharyngitis, meningoencephalitis, Legionnaire's disease and ear infections. Outbreaks of gastroenteritis, on the other hand, were attributed to *Giardia* and *Cryptosporidium,* as well as *E. coli, Shigella* and gastroenteritis of unknown origin.

Some autochthonous microbes have also been documented as agents of disease among humans. *Pseudomonas aeruginosa,* for example, had been reported in immuno-compromised patients, and was also detected in high numbers in faecal polluted recreational waters [69]. Utilizing such recreational areas, was found not only to be associated with enteric diseases, but also with upper respiratory infections. Cases of pneumonia have been attributed to *Staphylococcus aureus, Pseudomonas putrefaciens, Aeromonas hydrophila* and *Legionellae pneumophila.* Cases of skin infections were found to be caused by opportunistic spp. of *Aeromonas, Mycobacterium, Staphylococcus* and *Vibrio,* after swimming in contaminated recreational waters.

Sewage pollution may also influence the diversity of potential fungal pathogens that are known to infect humans and animals. Keratinophilic microbes occur in high numbers in sewage sludge since it contains high concentrations of keratin remnants [16]. These fungi, including the so-called dermatophytes are known as causative agents of a wide variety of cutaneous and subcutaneous mycoses. Awad and Kraume [23] found the following fungal species, retained in the following genera, in aerobic and anoxic sludge from wastewater plants in Berlin, Germany: *Chrysosporium, Microsporum, Trichophyton, Acremonium, Alternaria, Aspergillus, Candida, Chaetomium, Cladosporium, Fusarium, Geotrichum, Gliocladium, Gymnoascus, Mucor, Paecilomyces, Penicillium, Scopulariopsis, Sporothrix, Trichoderma* and *Verticillium.* It has been stated that the release of these fungi into the environment via activated sludge, presents an indisputable health risk [11, 23].
